A monitoring scan is performed in a contrast enhancement examination by an X-ray computed tomography imaging apparatus. In the monitoring scan, the X-ray computed tomography imaging apparatus monitors in real time the degree of dyeing with a contrast agent in a CT image, and when the pixel value of the CT image reaches a specific threshold, shifts to an actual scan (to be referred to as a post-contrast enhancement scan hereinafter). The monitoring scan is a scan mode for supporting the post-contrast enhancement scan. Thus, a set of the monitoring scan and post-contrast enhancement scan is performed. Condition setting of the monitoring scan and the like are performed immediately before executing the monitoring scan.
In some cases, a scan before injecting the contrast agent (to be referred to as a pre-contrast enhancement scan hereinafter) is performed in response to a clinical request. The pre-contrast enhancement scan is performed to acquire a subtraction image between a CT image acquired by the pre-contrast enhancement scan and a CT image acquired by the post-contrast enhancement scan.
FIG. 12 is a flowchart showing the typical sequence of a contrast enhancement examination according to a related art. FIG. 13 is a graph schematically showing the flow of the contrast enhancement examination according to the related art. As shown in FIGS. 12 and 13, a reference image acquisition scan is performed first (step SZ1). After the end of step SZ1, condition setting for the pre-contrast enhancement scan is performed (step SZ2). More specifically, in step SZ2, imaging conditions, reconstruction conditions, and the like are set. The pre-contrast enhancement scan is performed in accordance with the conditions set in step SZ2 (step SZ3). After performing step SZ3, condition setting for the monitoring scan and post-contrast enhancement scan is performed (step SZ4). By using a reference image acquired in step SZ1, an ROI (Region Of Interest) for the monitoring scan is set (step SZ5). After performing steps SZ4 and SZ5, a contrast agent is injected into a subject, and the monitoring scan is performed (step SZ6). If a pixel value in the ROI of the CT image acquired by the monitoring scan reaches a threshold, the post-contrast enhancement scan is performed (step SZ7). Then, the contrast enhancement examination ends.
ROI setting for the monitoring scan cannot be performed before the start of the pre-contrast enhancement scan. That is, the ROI setting has to be performed between the end of the pre-contrast enhancement scan and the start of the monitoring scan. Time is therefore taken for a shift from the pre-contrast enhancement scan to the monitoring scan. The conditions of the pre-contrast enhancement scan, monitoring scan, and post-contrast enhancement scan are set individually. For this reason, an error of the condition setting readily occurs. Also, the number of condition setting operations is large, and the working efficiency is poor.